Radial antenna and plasma processing apparatus comprising the same

ABSTRACT

Guide members ( 37 ) extending from the microwave entrance to a ring member ( 34 ) are arranged in the direction of propagation of microwave in a radial waveguide. The guide members ( 37 ) contribute to prevention of complex electromagnetic mode due to a microwave reflected from the peripheral portion of the radial waveguide. Therefore, a uniform plasma can be produced because the radiation into the process chamber is uniform even not by disposing any electromagnetic absorbing member at the peripheral portion of the radial waveguide. Since the microwave reflected from the peripheral portion of the radial waveguide can be used to produce a plasma if any electromagnetic absorbing member is not disposed, the plasma can be produced efficiently, and excessive heat is not generated.

BACKGROUND OF THE INVENTION

[0001] The present invention relates to a radial antenna and a plasmaprocessing apparatus using the same.

[0002] In the manufacture of a semiconductor device, plasma processingapparatuses are used often to perform processes such as formation of anoxide film, crystal growth of a semiconductor layer, etching, andashing. Among the plasma processing apparatuses, a microwave plasmaprocessing apparatus is available which produces a high-density plasmaby introducing a microwave into a process chamber through a radialantenna. According to the characteristic feature of the microwave plasmaprocessing apparatus, it has wide applications because it can stablyproduce a plasma even if the pressure of the plasma gas is comparativelylow.

[0003]FIG. 7 includes views showing the arrangement of an example of aradial antenna conventionally used in the microwave plasma processingapparatus. FIG. 7(a) is a longitudinal sectional view of the radialantenna, and FIG. 7(b) is a cross-sectional view taken along the lineVIIb-VIIb′ of FIG. 7(a).

[0004] As shown in FIG. 7(a), a radial antenna 130A conventionally usedin the plasma processing apparatus is formed of two parallel conductiveplates 131 and 132 which form a radial waveguide 133, and a ring member134 which connects the peripheral portions of the conductive plates 131and 132. A microwave entrance 135 is formed at the center of theconductive plate 132 to introduce a microwave from a microwave generator(not shown). The conductive plate 131 has a large number of slots 136,as shown in FIG. 7(b), to radiate the microwaves propagating in theradial waveguide 133 to a process vessel (not shown). The ring member134 is made of a conductor.

[0005] The microwaves introduced from the microwave entrance 135 areradiated little by little from the large number of slots 136 into theprocess chamber while the microwaves propagate radially from the centertoward the peripheral portion of the radial waveguide 133. Themicrowaves that have reached the peripheral portion of the radialwaveguide 133 are reflected by the ring member 134 to return toward thecenter of the radial waveguide 133. The microwaves are graduallyradiated through the large number of slots 136 into the process chamberwhile the microwaves propagate between the center and peripheral portionof the radial waveguide 133, so the microwaves are utilized forproducing the plasma.

[0006] While the microwaves reflect at the ring member 134 in the radialwaveguide 133, standing waves of a plurality of modes are formed, so acomplex electromagnetic mode is produced in the radial waveguide 133.Hence, radiation from the radial antenna 130A to the process chamberbecomes nonuniform, and a homogeneous plasma cannot be produced.

[0007]FIG. 8 includes views showing the arrangement of another exampleof the radial antenna conventionally used in the microwave plasmaprocessing apparatus. FIG. 8(a) is a longitudinal sectional view, andFIG. 8(b) is a cross-sectional view taken along the line VIIIb-VIIIb′.

[0008] A radial antenna 130B shown in FIG. 8 is an improvement over theradial antenna 130A shown in FIG. 7, in which an electromagneticabsorbing member 139 made of a carbon-containing ceramic material or thelike is applied to the inner wall of a ring member 134. Theelectromagnetic absorbing member 139 absorbs most of the microwaves thathave reached the peripheral portion of a radial waveguide 133, so themicrowaves are not substantially reflected toward the center of theradial waveguide 133. Accordingly, no complex electromagnetic mode isformed in the radial waveguide 133. Radiation toward the process chamberbecomes uniform, so a homogeneous plasma can be produced.

[0009] With the conventional radial antenna 130B shown in FIG. 8, themicrowaves absorbed by the peripheral portion of the radial waveguide133 cannot be utilized for producing the plasma. The plasma productionefficiency is thus poor. Since the electromagnetic absorbing membergenerates heat upon absorption of the microwaves, the peripheral portionof the radial waveguide 133, particularly the ring member 134, islocally heated to deform undesirably.

SUMMARY OF THE INVENTION

[0010] The present invention has been made to solve the above problems,and has as its object to improve the plasma uniformity withoutsacrificing the plasma production efficiency or generating extra heat.

[0011] In order to achieve the above object, a radial antenna accordingto the present invention is characterized in that it has a guide memberin the direction of propagation of the microwave from the microwaveintroducing portion to the radiating portion.

[0012] More specifically, the radial antenna comprises a firstconductive plate having a plurality of slots, a second conductive platehaving a microwave entrance and arranged to oppose the first conductiveplate, a ring member which connects peripheral portions of the first andsecond conductive plates, and a guide member arranged in a radialwaveguide formed of the first and second conductive plates to extend ina direction of propagation of a microwave from the microwave entrance tothe ring member.

[0013] The guide member can suppress generation of a standing wave atleast in the circumferential direction of the radial waveguide, and canprevent production of complex electromagnetic mode due to a microwavereflected from the peripheral portion of the radial waveguide. Hence, noelectromagnetic absorbing member need be provided to the peripheralportion of the radial waveguide. The microwaves reflected from theperipheral portion of the radial waveguide are also radiated through theslots formed in the first conductive plate, so the microwaves contributeto production of a plasma. Since no electromagnetic absorbing memberneed be provided, excessive heat is not generated.

[0014] In this radial antenna, the guide member may comprise a pluralityof conductive partitions arranged in the radial waveguide radially whenviewed from the top and extending between the first and secondconductive plates.

[0015] A gap between adjacent ones of the partitions is preferably setto not less than a length corresponding to a substantial half-wavelength of a microwave propagating in the radial waveguide. With thissetting, the microwave can easily pass through a region sandwiched bythe partitions.

[0016] A gap between adjacent ones of the partitions is preferably setto less than a length corresponding to substantial one wave length ofthe microwave. With this setting, standing waves of a plurality of modesdo not mixedly exist in the region sandwiched by the partitions. Hence,no complex electromagnetic mode is produced in this region.

[0017] Each of the partitions may have a linear planar shape, or mayhave such a shape that a side thereof which is close to the ring membermay be arcuate in the same direction as an inner periphery of the ringmember.

[0018] The partitions are arranged radially, preferably to keep awayfrom the slots formed in the first conductive plate. When the partitionsare arranged in this manner, radiation through the respective slots willnot be interfered with by the partitions.

[0019] The microwave entrance is preferably formed at a center of thesecond conductive plate. The microwave may be introduced to themicrowave entrance by a coaxial line, or by a cylindrical waveguide.

[0020] A plasma processing apparatus according to the present inventionis characterized by comprising a susceptor which places a target objectthereon, a process chamber which accommodates the susceptor, exhaustmeans for evacuating an interior of the process chamber, gas supplymeans for supplying a gas into the process chamber, and antenna meanswhich is arranged to oppose a surface of the susceptor where the targetobject is to be placed and which supplies a microwave into the processchamber, wherein the antenna means comprises the radial antennadescribed above.

BRIEF DESCRIPTION OF THE DRAWINGS

[0021]FIG. 1 is a view showing the arrangement of an etching apparatusaccording to the first embodiment of the present invention;

[0022]FIG. 2 is a sectional view showing an arrangement of a radialantenna;

[0023]FIG. 3 is a view for explaining how to set the gap between theadjacent partitions in FIG. 2;

[0024]FIG. 4 is a sectional view showing a modification of thepartitions;

[0025]FIG. 5 is a sectional view showing another arrangement of theradial antenna;

[0026]FIG. 6 is a view for explaining how to set the gap between theadjacent partitions in FIG. 5;

[0027]FIG. 7 includes views showing an example of a radial antennaconventionally used in a plasma processing apparatus;

[0028]FIG. 8 includes views showing another example of the radialantenna conventionally used in the plasma processing apparatus;

[0029]FIG. 9 is a view showing the arrangement of an etching apparatusaccording to the third embodiment of the present invention; and

[0030]FIG. 10 is an enlarged sectional view showing the portionsurrounded by a broken line in FIG. 9.

DETAILED DESCRIPTION OF THE INVENTION

[0031] The embodiments of the present invention will be described indetail with reference to the accompanying drawing. A description will bemade by way of examples in which a plasma processing apparatus using aradial antenna according to the present invention is applied to etchingapparatuses.

[0032] First Embodiment

[0033]FIG. 1 is a view showing the arrangement of an etching apparatusaccording to the first embodiment of the present invention. In FIG. 1,the sectional structure of part of the arrangement is shown.

[0034] The etching apparatus shown in FIG. 1 has a cylindrical processchamber 11 with an upper opening. This process chamber 11 is made of aconductive material such as aluminum.

[0035] Exhaust ports (exhaust means) 14 communicating with a vacuum pump(not shown) are formed in the bottom of the process chamber 11, and canevacuate the interior of the process chamber 11 to a predeterminedvacuum degree.

[0036] A plasma gas supply nozzle 15 for introducing a plasma gas suchas Ar into the process chamber 11, and a process gas supply nozzle 16for introducing an etching gas are formed in the upper and lowerportions, respectively, of the side wall of the process chamber 11. Thenozzles (gas supply means) 15 and 16 are formed of quartz pipe or thelike.

[0037] A susceptor 22 for placing an etching target substrate (targetobject) on its upper surface is accommodated in the process chamber 11,and is fixed on a support table 23 which is fixed to the bottom of theprocess chamber 11 through an insulating plate 24. The susceptor 22 isalso connected to a bias RF power supply 26 through a matching box 25.

[0038] A flat plate-like dielectric plate 13 is horizontally arranged inthe upper opening of the process chamber 11. A quartz glass or ceramic(e.g., Al₂O₃ or AlN) plate with a thickness of about 20 mm to 32 mm isused as the dielectric plate 13. A seal member 12 such as an O-ring isdisposed at the bonding portion of the process chamber 11 and dielectricplate 13. This assures the hermeticity in the process chamber 11.

[0039] A radial antenna 30 is disposed on the dielectric plate 13 withits radiating portion (conductive plate 31 to be described later) facingdown. The radial antenna 30 is an antenna means that supplies microwavesMW into the process chamber 11 through the dielectric plate 13. Thedielectric plate 13 is arranged to oppose the radiating portion of theradial antenna 30, and covers the radiating portion entirely. Hence, theradial antenna 30 is protected from the plasma produced in the processchamber 11. The circumferential surfaces of the dielectric plate 13 andradial antenna 30 are covered by a shield material 17.

[0040] The radial antenna 30 is formed of the first conductive plate 31which forms the radiating portion, a second conductive plate 32 arrangedabove the conductive plate 31 to oppose it, a ring member 34 forconnecting the peripheral portions of the conductive plates 31 and 32,and a plurality of partitions 37 arranged in a radial waveguide 33formed of the two conductive plates 31 and 32. The radial antenna 30with this arrangement has a cylindrical shape with the plurality ofpartitions 37 being arranged in it. The conductive plates 31 and 32,ring member 34, and partitions 37 are made of a conductor such as copperor aluminum. No electromagnetic absorbing member is attached to theinner wall of the ring member 34, unlike in the conventional radialantenna 130B shown in FIG. 8.

[0041] A microwave entrance 35 as the introducing portion of themicrowave MW is formed at the center of the conductive plate 32. Theconductive plate 31 which forms the radiating portion has a large numberof slots 36.

[0042] A coaxial line 41 is connected to the center of the radialantenna 30. An outer conductor 41A of the coaxial line 41 is connectedto the microwave entrance 35 of the conductive plate 32. The distal endof a central conductor 41B of the coaxial line 41 has a circular conicalshape, the bottom of which is connected to the center of the conductiveplate 31.

[0043] The coaxial line 41 connected to the radial antenna 30 in thismanner is connected to a microwave generator 45 through a rectangularcoaxial converter 42 and rectangular waveguide 43. For example, themicrowave generator 45 generates a microwave MW of 2.45 GHz. Thefrequency of the microwave MW suffices as far as it falls within therange of 1 GHz to 10-odd GHz. A matching circuit 44 for impedancematching is provided midway along the rectangular waveguide 43, so thepower use efficiency can be improved.

[0044] Alternatively, the microwave generator 45 and the microwaveentrance 35 of the radial antenna 30 may be connected by a cylindricalwaveguide.

[0045]FIG. 2 is a sectional view of the radial antenna 30, and shows asection taken along the line II-II′ of FIG. 1. The slots 36 formed inthe conductive plate 31 are concentrically formed in a large number, asshown in FIG. 2. The pitch among the slots 36 in the radial direction isset on the basis of a wavelength λg of the microwave MW in the radialwaveguide 33. To realize a so-called radial antenna, the pitch is set toalmost a length corresponding to λg. To realize a so-called leaky-waveantenna, the pitch is set to almost a length corresponding to λg/20 toλg/30.

[0046] The eight partitions 37 are formed in that region of the radialwaveguide 33 which is close to the peripheral portion, to keep away fromthe slots 36. Each partition 37 is arranged in the direction ofpropagation, from the microwave entrance 35 to the ring member 34, ofthe microwave MW. More specifically, the respective partitions 37 have alinear planar shape when viewed from the top, and are equiangularlydistributed radially with respect to a center C of the radial waveguide33. One end of each partition 37 is connected to the ring member 34.These partitions 37 extend between the conductive plates 31 and 32 tohave the same heights as that of the ring member 34, as shown in FIG. 1,and divide that region of the radial waveguide 33 which is close to itsperipheral portion into eight, as shown in FIG. 2. As described above,the partitions 37 are arranged to keep away from the slots 36, so anelectric field as designed can be radiated through the slots 36.

[0047] The thickness of each partition 37 is about 1 mm to 3 mm. Theinner and outer peripheral portions of each partition 37 shown in FIG. 2have the same thickness, but they may be different. For example, theouter peripheral portion may be formed thicker than the inner peripheralportion.

[0048] The ring member 34 shown in FIG. 2 has a circular shape.Alternatively, those portions of the ring member 34 which are betweenthe adjacent partitions 37 may be linearly formed, so the entire ringmember 34 forms a polygonal shape.

[0049]FIG. 3 is a view for explaining how to set the gap between theadjacent partitions 37. Since the microwave entrance 35 is formed at thecenter of the conductive plate 32, the gap between adjacent partitions37A and 37B is defined as a distance between the surfaces of thepartitions 37A and 37B in a direction perpendicular to the direction ofpropagation of the microwave MW in the radial waveguide 33. In thiscase, the gap between the adjacent partitions 37A and 37B is preferablyset to almost satisfy L1≧λg/2 and L2≧λg. If L1 becomes less than λg/2,the microwave MW becomes difficult to pass. If L2 is less than λg,standing waves of the plurality of modes can be prevented from beingmixedly present in the region sandwiched by the partitions 37A and 37B.

[0050] A delay member (not shown) made of a dielectric material with arelative dielectric constant of larger than 1, e.g., a ceramic material,may be arranged in the radial waveguide 33.

[0051] The operation of the etching apparatus shown in FIG. 1 will bedescribed.

[0052] With the substrate 21 being placed on the upper surface of thesusceptor 22, the interior of the process chamber 11 is set to a vacuumdegree of, e.g., about 0.01 Pa to 10 Pa. While maintaining this vacuumdegree, Ar is supplied as the plasma gas from the plasma gas supplynozzle 15, and an etching gas such as CF₄ is supplied from the processgas supply nozzle 16 under flow rate control.

[0053] With the plasma gas and etching gas being supplied into theprocess chamber 11, the microwave MW from the microwave generator 45 issupplied to the radial antenna 30 through the rectangular waveguide 43,rectangular coaxial converter 42, and coaxial line 41.

[0054] The microwave MW supplied to the radial antenna 30 spreadsradially from the center in the radial waveguide 33 formed of theconductive plates 31 and 32. The partitions 37 arranged in that regionof the radial waveguide 33 which is close to its peripheral portionserve as the guide members, so the microwaves MW propagate along thepartitions 37. Since the gap between the adjacent partitions 37 is setto almost L1≧kg/2, the microwave MW can easily propagate in the regionpartitioned by the partitions 37.

[0055] Since no electromagnetic absorbing member like the conventionalone shown in FIG. 8 is attached to that inner wall of the ring member 34which serves as the peripheral portion of the radial waveguide 33, themicrowaves MW that have reached the peripheral portion of the radialwaveguide 33 are totally reflected there and are directed toward thecenter of the radial waveguide 33 along the partitions 37. Themicrowaves MW are radiated little by little through the large number ofslots 36 while propagating between the center and peripheral portion ofthe radial waveguide 33. Therefore, in the radial antenna 30, not onlythe microwaves MW directed from the center toward the peripheral portionof the radial waveguide 33 but also the microwaves reflected from theperipheral portion are radiated through the slots 36.

[0056] The microwaves MW radiated from the radial antenna 30 aretransmitted through the dielectric plate 13 and are introduced into theprocess chamber 11. The microwaves MW form an electric field in theprocess chamber 11 to ionize Ar, thus producing a plasma in a space S1above the substrate 11 as the processing target.

[0057] In this etching apparatus, since the susceptor 22 is biased witha negative potential, ions are extracted from the produced plasma toetch a substrate 21.

[0058] In this radial antenna 30, the microwaves MW reflected from theperipheral portion of the radial waveguide 33 are also radiated throughthe slots 36, as described above. As the microwaves MW reflected fromthe peripheral portion can also be utilized to produce the plasma, theplasma can be efficiently produced in the same manner as in the priorart shown in FIG. 7.

[0059] In that region in the radial waveguide 33 which is divided by thepartitions 37, the microwaves MW directed toward the peripheral portionof the radial waveguide 33 and the microwaves MW reflected and directedtoward the center form a standing wave. Since the gap between theadjacent partitions 37 is set to almost L2<λg, standing waves with aplurality of modes are not mixedly present in this region. Hence, acomplex electromagnetic mode is not produced in this region. Therefore,as this radial antenna 30 can perform uniform radiation in the samemanner as in the prior art shown in FIG. 8, it can produce a uniformplasma.

[0060] In this radial antenna 30, since no electromagnetic absorbingmember is attached to the inner wall of the ring member 34, as describedabove, the ring member 34 will not be heated to deform.

[0061] In this manner, when the radial antenna 30 is used, the plasmauniformity can be improved without sacrificing the plasma productionefficiency or generating extra heat.

[0062] In FIG. 2, the partitions 37 with the linear planar shape whenviewed from the top are arranged radially. Alternatively, as shown inFIG. 4, partition plates 39 with such planar shapes that their sidesclose to the ring member 34 are arcuate in the same direction as theirinner peripheral portions may be arranged radially.

[0063] In this embodiment, the eight partitions 37 are arrangedradially. The number of partitions 37 is not limited to eight, butsuffices as far as it is approximately a number obtained by dividing theinner circumferential length of the ring member 34 by λg.

[0064] Second Embodiment

[0065]FIG. 5 is a sectional view showing an arrangement of a radialantenna with an open area larger than that of the radial antenna 30shown in FIGS. 1 and 2, and shows a section corresponding to FIG. 2.FIG. 6 is a view for explaining how to set the gap between adjacentpartitions. In FIGS. 5 and 6, the same portions as in FIGS. 2 and 3 aredenoted by the same reference numerals, and a description thereof willbe omitted as required.

[0066] When a radial antenna 30A with a large open area is to be formed,a gap L2 between adjacent partitions 37A and 37B sometimes satisfiesL2≧λg, as shown in FIG. 6. In this case, another partition 38 may bearranged at part of the region where the gap L2 of the partitions 37Aand 37B satisfies L2≧λg. At this time, the gaps among the partitions 37Aand 37B, and 38 are set to approximately satisfy L3≧λg/2 and L4<λg.

[0067] When a radial antenna with a much larger open area is to beformed, other partitions may be arranged one after another amongadjacent partitions in accordance with the conditions described above.

[0068] Then, a uniform plasma can be efficiently produced in the samemanner as in the radial antenna 30 shown in FIGS. 1 and 2, and thermaldeformation of a ring member 34 can be prevented.

[0069] In the above description, a plasma processing apparatus using aradial antenna according to the present invention is applied to etchingapparatuses. The present invention can also naturally be applied toother plasma processing apparatuses such as a plasma CVD apparatus.

[0070] Third Embodiment

[0071]FIG. 9 is a view showing the arrangement of an etching apparatusaccording to the third embodiment of the present invention. In FIG. 9,the same portions as in FIG. 1 are denoted by the same referencenumerals, and a description thereof will be omitted as required. FIG. 10is an enlarged sectional view showing a portion X surrounded by a brokenline in FIG. 9. For the sake of descriptive convenience, the gap betweena dielectric plate 13 and radial antenna 30 is exaggerated.

[0072] In the etching apparatus shown in FIG. 9, a distance D from theinner surface of a ring-like shield material 17 to the inner surface ofthe side wall of a process chamber 11A is set to a length correspondingto almost N/2 times (N is a natural number) a wavelength λg of amicrowave MW in a space (a satin finish region in FIG. 10 which includesthe dielectric plate 13) 18 which is formed between the upper surface ofthe side wall of the process chamber 11A and the radial antenna 30. Theposition to arrange the shield material 17 is determined by consideringthe relative dielectric constant of a member that forms the space 18,e.g., the dielectric plate 13.

[0073] A ring-like seal member 12 which is present at the bondingportion of the upper surface of the side wall of the process chamber 11Aand the dielectric plate 13 and hermetically seals the bonding portionis arranged in the vicinity of a position which is away from the innersurface of the shield material 17 by a length corresponding to M×λg/2 (Mis a natural number of N or less). At this time, it suffices if the sealmember 12 is arranged at a position which avoids a position ofapproximately (2M+1)λg/4 from the inner surface of the shield material17. The seal member 12 is preferably arranged at a position of M×λg/2times. The position to arrange the seal member 12 is also determined byconsidering the relative dielectric constant of the member that formsthe space 18.

[0074] Of the microwaves MW introduced from the radial antenna 30 intothe process chamber 11A through the dielectric plate 13, some do notcontribute to plasma production but repeat irregular reflection in theprocess chamber 11A. Some of such microwaves MW enter the space 18formed between the upper surface of the side wall of the process chamber11A and the radial antenna 30. The microwaves MW that have entered thespace 18 are reflected by the shield material 17. Hence, a standing waveas shown in FIG. 10 is formed in the space 18.

[0075] In the conventional etching apparatus, since the distance D isarbitrarily set, it is sometimes approximately λg/4, or 3λg/4. In thiscase, the position of the inner surface of the side wall of the processchamber corresponds to the antinode of the standing wave formed in thespace 18, so the potential at the inner surface of the side wall of theprocess chamber increases, sometimes causing abnormal discharge at thisposition.

[0076] This abnormal discharge damages the side wall of the processchamber. Fine dust generated upon this damage contaminates the interiorof the process chamber.

[0077] If a seal member such as an O-ring is arranged at a positionwhich is away from the inner surface of the shield member byapproximately λg/4 or 3λg/4, the strong electromagnetic field of thestanding wave damages the seal member to shorten its service life.

[0078] In the etching apparatus shown in FIG. 9, since the distance D isset to approximately N×λg/2, the position of the inner surface of theside wall of the process chamber 11A corresponds to the node of standingwave formed in the space 18. Hence, the potential at the inner surfaceof the side wall of the process chamber 11A becomes zero, so no abnormaldischarge occurs at this position. Therefore, contamination in theprocess chamber 11A by abnormal discharge can be suppressed.

[0079] The seal member 12 is arranged in the vicinity of a position awayfrom the inner surface of the shield material 17 by M×λg/2. As theelectromagnetic field at this position is weak, damage to the sealmember 12 by the electromagnetic field can be suppressed, so the servicelife of the seal member 12 can be prolonged.

[0080] In this embodiment, the description has been made by way ofexamples in which a plasma processing apparatus according to the presentinvention is applied to etching apparatuses. The present invention canalso naturally be applied to other plasma processing apparatuses such asa plasma CVD apparatus. The present invention can be applied not only toa microwave plasma processing apparatus but also to, e.g., an ECR(Electron Cyclotron Resonance) plasma processing apparatus.

1. A radial antenna characterized by comprising a first conductive platehaving a plurality of slots, a second conductive plate having amicrowave entrance and arranged to oppose said first conductive plate, aring member which connects peripheral portions of said first and secondconductive plates, and a guide member arranged in a radial waveguideformed of said first and second conductive plates to extend in adirection of propagation of a microwave from said microwave entrance tosaid ring member.
 2. A radial antenna according to claim 1.characterized in that said guide member comprises a plurality ofconductive partitions arranged in the radial waveguide radially whenviewed from the top and extending between said first and secondconductive plates.
 3. A radial antenna according to claim 2,characterized in that a gap between adjacent ones of the partitions isnot less than a length corresponding to a substantial half-wave lengthof a microwave propagating in the radial waveguide.
 4. A radial antennaaccording to claim 2, characterized in that a gap between adjacent onesof the partitions is less than a length corresponding to substantial onewave length of the microwave.
 5. A radial antenna according to claim 2,characterized in that each of the partitions has a linear planar shape.6. A radial antenna according to claim 2, characterized in that each ofthe partitions has such a shape that a side thereof which is close tosaid ring member is arcuate in the same direction as an inner peripheryof said ring member.
 7. A radial antenna according to claim 2,characterized in that the partitions are arranged to keep away from theslots.
 8. A radial antenna according to claim 1, characterized in thatthe microwave entrance is formed at a center of said second conductiveplate.
 9. A radial antenna characterized in that a guide member isformed to extend in a direction of propagation of the microwave from aninlet portion to a radiating portion of a microwave.
 10. A plasmaprocessing apparatus characterized by comprising a susceptor whichplaces a target object thereon, a process chamber which accommodatessaid susceptor, exhaust means for evacuating an interior of said processchamber, gas supply means for supplying a gas into said process chamber,and antenna means which is arranged to oppose a surface of saidsusceptor where the target object is to be placed and which supplies amicrowave into said process chamber, wherein said antenna meanscomprises the radial antenna according to claim 1.